Guarantees (Details 3)	Mar. 31, 2017 USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 92,800,000
Fixed maximum amounts guaranteed by year 2017	8,300,000
Fixed maximum amounts guaranteed by year 2018	26,200,000
Fixed maximum amounts guaranteed by year 2019	54,300,000
No scheduled maturity date	4,000,000
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit	31,000,000
Letters of credit set to expire - 2017	30,300,000
Letters of credit set to expire - 2018	700,000
Outstanding letters of credit	0
Amount of surety bonds outstanding	744,000,000
Financial guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 62,600,000